Beam deflection tube having parallel focusing and beam defining plates



Feb. 11, 1947. NIH. GREEN HAL 2,415,481

BEAM DEFLECTION TUBE HAVING PARALLEL FOCUSING AND BEAM DEFINING PLATES Filed June so, 1943 2 Sheets-Sheet 1 Feb. 11, 1941i N. H. GREEN ETAL 2,415,481

BEAM DEFLECTION TUBE HAVING PARALLEL FOCUSING AND BEAM DEFINING PLATES Filed June 30, 1943 I 2 Sheets-Sheet 2 Patented Feb. 11, 1947 BEAM DEFLECTION TUBE nsvnzo PARAL- LEL FOCUSING AND BEAM PLATES DEFINING Norval H. Green, Hasbrouck Heights, and William Hoyt Warren, Montclair, N. .l., assignors to Radio Corporation of America, a corporation of Delaware Application June 30, 1943, Serial No. 492,808

14 Claims.

Our invention relates to electron discharge devices, more particularly to such devices suitable for use at ultra high frequencies and utilizing a beam of electrons which is periodically deflected for varying the output current of the device.

Electron discharge devices to which the present invention is directed, are used as mixers and amplifiers, particularly at high frequencies where advantages of low input conductance and capacity are especially important. One form of beam deflection tube includes a cathode and associated elements for providing a directed beam of electrons of rectangular cross-section, which beam is directed toward a-collector through a beam deflection electrode system, the electron beam being deflected across an aperture to determine the amount of current going to the collector. Positioned between the cathode and collector is an electron lens and beam deflection electrode assembly. It comprises a cylinder coaxial with and surrounding the beam path. At one end of the cylinder is positioned a transverse partition provided with apertures through which the beam is directed. A second and similar transverse apertured partition is provided at the other end of the cylinder, the aperturesin the two partitions being aligned. The aperture in the second partition is bisected by means of a rod-like element positioned centrally of the aperture, thus producing in efiect a double aperture. A third partition, also apertured, is positioned between the other two partitions and its aperture must also be properly aligned with the other apertures. These partitions may be in the form of shallow caps, the lips of which are welded to the cylinder. A pair of deflecting electrodes are mounted within the cylinder and between the second and third apertured partitions for deflecting the beam of electrons across the double aperture. The

potential difierence between the deflecting plates and the third apertured partition forms an electron lens which focuses the rectangular beam in the plane of the aperture in the end partition in the cylinder. The collector is coated with secondary electron emitting material and is maintained at a lower potential than the deflecting electrode assembly. The cylinder collects the secondary electrons. Current in the collector or secondary emitter circuit is then proportional to the difierence between the secondary charges drawn back to the cylinder and the number of electrons in the primary or incident beam. A tube of this kind is described in Patent 2,294,659 Herold, assigned to the same assignee as the present application.

As pointed out above, for some cases a small wire is centered along the major axis of the last aperture and a cross bias between the deflecting plates is provided to center the beam on this wire so that with zero signal the beam is effectively blocked from the secondary emitter. When an alternating signal is applied between the deflecting plates, the beam is deflected to either side or the center, while causing the secondary emitter or output current to rise sharply as the beam leaves the blocking wire. Since the transconductance of the device is given by the slope 01' the output current-deflecting voltage characteristic, it is essential that for best sensitivity the three apertures, center wire and deflecting plates be perrectly aligned so that the beam is completely blocised at zero signal and so that it will leave the wire abruptly as the signal is applied. Small deviations from the true rotational or axial alignment of these parts will distort the output current characteristic such that the tube may beinoperative. To maintain the required alignment, each aperture must be formed to center with the edges of the cupshaped partition, then the cups must be carefully centered in the cylinder for rotational alignment before they are welded. This results in a slow and tedious assembly for manufacture.

it is, therefore, an object or our invention to provide an improved design of an electron discharge device particularly suitable for use at ultra high frequencies and utilizing a beam of electrons periodically deflected to vary the output of the device.

Another object of our invention is to provide a device of the kind describedin which greater uniformity or" characteristics between devices is obtained.

Another object of our invention is to provide such a device of improved and simplified constructionwhich can be easily and quickly assembled and in which alignment of various electrodes and apertures in the electrode assembly is assured. g

A still further object of our invention is to provide a novel construction for forming electron lens systems and beam forming and controlling electrode assemblies in electron discharge devices utilizing electron beams.

The novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawings in which Figure 1 is a side elevation of an electron discharge device made according to our invention but with the base removed and parts in section; Figure 2 is a top View of Figure 1; Figure 3 is a section taken along the line 3--3 of Figure 1; Figure 4 is a section taken along the line 4-4 of Figure 2; Figure 5 is a schematic diagram of an electron discharge device made according -to our invention and its associated circuit; Figure 6 is an exploded perspective V ew of the electrode mount assembly utilized in the device shown in Figures 1 to 4, inclusive, and Figure 7 shows details of construction.

In Figure 1 an electron discharge device made according to our invention includes an evacu ated envelope I0 having within it the mount assembly mounted between the insulating spacer members H and I 2, preferably of mica, which are supported from various leads from the press and base, not shown. The cathode assembly comprises the indirectly-heated cathode 43 provided with heater wires M and J5, one'o-f which may alsorserve as the "cathode lead and the beam forming and beam directing shielding electrode P6 surrounding the cathode onthree sides. shield maybe provided with the lead -11 so that it may be-biased eta-different potential from the cathode. -Mounted at the other end of the envelope is the collector-or secondary emitting electrode [8, which is inthe form of aloop and provided with a secondary emitting shell or coating 19, this electrode being supported by lead and support wire MI.

Mounted between the cathode and the collector or secondary emitting electrode is the beam focusing and deflecting electrode assembly depressions 2i and 22' which provide aperture ribs between which theelectron beam passes and by which the beam current is limited. These ribs registerwith the notched portions 35' and 36 of the spacer plates 35 and .36. Deflecting plates 25 and 8 are mounted within the apertures :23 and 24of the side platesand supribnted in position by mica straps. 21 and 28 provided with apertures 27' and 28' through which tabs -25' and 26 on the plates extend. These mica straps are secured to the side plates by means of tabs Hand .30 fastened to the side plates so that the deflecting electrodes are mounted in insulating relationship with the side plates 2| and 22. These side plates are provided with lead wires 3| and 3.2 for applying the desired alternating potentials to the deflecting plates. .The

side plates and deflectingelectrodes during operation provide a lens system for focusing thebeam on'rocl-like element 33.

Mounted at the end of theside plates 2! and 22 and spaced from theplates but between, the

-- plates to provide a double aperture, is the rodlike conducting element or wire 33 supported between the plates as best shownin Figures 2 -and-3 and Figure 7, by means of the clips 34. and

34', which center the rod and maintain it in spaced relationship with the surfaces of the side plates so as-to provide a double aperture. Thus "a beam directed from the cathode passes between 4 the side plates, through the passageway provided by the spacing plates 25 and 26, between the aperture ribs 21 and 22 and deflecting plates 25 and 23 which deflect the beam across the Wire 33 .to the secondary emitting surface IQ of eleotrocle 48, the secondary emission electrons being collected by the side plates of the deflecting electrode mount assembly.

In assembly the side plates 2| and 22 and separating plates 35 and 36 can be quickly stacked upon each other in a jig provided for this purpose and quickly welded. The result is perfect alignment of the parts.

Rapid assembly is obtained simply by threading the side plates and separators over a rectangular center post in the welding jig provided for this purpose. The center post may be dimensioned to provide a slip fit with the portions of the plates and separators blanked for the deflecting plates, and the assembly is welded before removing from the jig.

Positioning the wire 33 and clips 34 and '34 between the ends of the side plates 2'1 and 22 automatic-ally aligns the wire with the longitudin-al axis of the deflecting electrode assembly. The ribs 2| and 22', which are pre-stamped in the side plates, provide-a limiting aperture. In order to narrow the beam width to any desired value, one or-more pairs of ribs may be used.

Accurate centering of the wire'in the last apertures is obtained by setting the strip thickness of the clip 34 to where T is equal to the thickness of the separator plate and D is equal to the center wire diameter. The deflecting plates are then positioned in the blanked windows of the partial mount and'positioned in the plane of the side plates by clips which engage the supporting 'm'icas 27 and 28 and whichare fastened 'to the side plates. The

cathode shield, cathode, partial mount assembly than the deflecting electrode assembly.

Thuswith theirhp'rdvedmount'design for beam deflection "tubes, automatic alignment of apertures and -center'wire is provided'andthis obvi- "ates the need 'for several 'of the parts required for previous designs. Rapid as'semb'lyis insured aswell' as accurate'positionin'g'of all'parts. Since automatic alignment results, characteristics are more uniform. I

The flat element's which'permit stacking obviate the necessity for prefabricating individual apertures to the critical dimensions der'nan'dedfor the cylindrical structure; fiat structures permit higher assembly speeds for stacking and welding, and accurate rotational and axial alignment of the apertures, deflecting plates and center wire is insured by the new construction andwithout resorting to-the unwieldy methods necessary to obtain this alignment in previous designs.

' While we have indicated the preferred embodiments of our invention of which we are now aware and have also indicated only one specific application for which our invention may be employed,

it will be apparent that our invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used andthe purpose for which it is employed without departing from the scope of our invention as set forth in the appended claims.

What we claim-as new is:

1. An electron discharge device having means for providing a beam of electrons, means for receiving said electrons, means positioned between said beam providing means and said receiving means and through which the beam of electrons passes during operation of said electron discharge device, and including a pair'of conducting platelike members spaced apart to provide a passageway therebetween, means on said plate-like member extending toward each other for restricting said passageway, said plate-like members having oppositely disposed apertures and deflecting electrodes positioned within said apertures.

2. An electron discharge device having means for providing a beam of electrons, means for receiving said electrons, means positioned between said beam providing means and said receiving means and through which the beam of electrons passes during operation of said electron discharge device, and including a pair of conducting platelike members spaced apart to provide a passageway therebetween, said plate-like members having oppositely disposed apertures, and deflecting electrodes positioned within said apertures.

3. An electron discharge device having means for providing a beam of electrons, means for receiving said electrons, means positioned between said beam providing means and said receiving means and through which the beam of electrons passes during operation of said electron discharge device, and including a pair of conducting platelike members spaced apart to provide a passageway therebetween, said plate-like members having oppositely disposed apertures, deflecting electrodes positioned within said apertures, and a rod-like element at one end of said plate-like members and positioned between the ends of said plate-like members and in spaced relationship.

4. An electron discharge device having a cathode for supplying a directed beam of electrons,

and anotherelectrode for receiving said electrons, and means positioned between said cathode and said receiving electrode and including an electrode assembly for periodically deflecting said electron beam and including a pair of spaced parallel side plates provided with oppositely disposed registering apertures, and depressed portions in said plates extending toward each other and in registering relationshi for providing a restricted aperture between said plates, a pair of separating elements positioned at opposite edges of said plates for maintaining said plates in spaced relationship, and deflecting electrodes positioned within the apertures in the side plates.

5. An electron discharge device having a cathode for supplying a directed beam of electrons, and another electrode for receiving said electrons, and means positioned between said cathode and said receiving electrode and including an elec-- trode assembly for periodically deflecting said electron beam and including a pair of spaced parallel side plates provided with oppositely disposed registering apertures, and depressed pertions in said plates extending toward each other and in registering relationship for providing a restricted aperture between said plates, a pair of separating elements positioned at opposite edges of said plates and having recessed portions on the inner edges thereof registering with said depressed portions and other recessed portions registering with the apertures in said side plates, and a rodlike element positioned at one end of the plates and centrally of the space between said plates, and deflecting electrodes positioned Within the apertures inthe side plates.

6. An electron discharge device having a oath ode for supplying a directed beam of electrons, a shield partially surrounding said cathode, and another electrode for receiving said electrons, and means positioned between said cathode and said receiving electrode and including an electrode assembly for periodically deflecting said electron beam and including a pair of spaced parallel side plates provided with oppositely disposed -registering apertures and depressed portions Within said plates extending toward each other and in registering relationship for providing a restricted aperture between said plates, a pair of separating elements positioned at opposite edges of said plates and having recessed portions on the inner edges thereof registering with said depressed portions, and other recessed portions registering with the apertures in said side plates, and a rod-like element positioned at one end of the plates and centrally of the space between said plates and deflecting electrodes positioned within the apertures in the side plates and supported therein by insulating members secured to said plates.

'7. An electron discharge device having a cathode for supplying a directed beam of electrons, and another electrode for receiving said electrons, and means positioned between said cathode and said receiving electrode and including an electrode assembly for periodically deflecting said electron beam and including a pair of spaced parallel side plates provided with oppositely disposed registering apertures, a pair of separating elements positioned at opposite edges of said plates and having recessed portions on the inner edges thereof registering with the apertures in said side plates, and a rod-like element at one end of said plates and positioned centrally of the space between said side plates, and conducting loops surrounding the rod-like element at the ends of said element for supporting and spacing said element from said plates, and deflecting electrodes positioned within the apertures in the side plates.

8. An electron discharge device having a cathode for supplying a directed beam of electrons and another electrode for receiving said electrons, and means positioned between said cathode and said receiving electrode and including an electrode assembly for periodically deflecting an electron beam and through which said beam is directed, and including a pair of spaced parallel conducting side plates provided with oppositely disposed registering apertures, a pair of separating elements positioned at opposite edges of said side plates for maintaining said side plates in spaced relationship and deflecting electrodes po sitioned within the apertures in said sideplates.

9. An electron discharge device having means for providing a beam of electrons, means for receiving said electrons, means positionedbetween said beam providing means and said receiving means and through which the electrons pass during operation of said electron discharge device,

:andiin'cluding a .pair of plateelike members :lying in parallel planes and spaced apart to :provide a passageway"therebetween,means on said platelike members extending toward each other =for restricting said passageway,:said plate-like members having deflecting electrodes associated therewith and lying in planes parallel to the planes in which said' plates lie, and positioned' between the restricted passageway and said receiving means, 1 r 1 '10. An electron discharge device having a cathode for supplying a :directed vbeam .of :=electrons and another electrode for receiving said electrons, and means positioned between said cathode and the receivingelectrode-and including an electrode assembly farperiodicallydefiecting said= electron beam, and includinga pair of spaced parallel conducting side plates, and meanson said :plates extending toward'each other and in registering relationship for providing a restricted aperture betweensaid plates,- and separating -elements positioned on opposite edges of saidplates for maintaining said plates inspacedrelationship, and deflecting electrodes associated with said plates and positioned between the restricted aperture and the receiving electrode, the beam path passing throughthe restricted aperture and between the deflecting electrodes.

11. An electron dischargedevice having means for providing a beam of electrons, :means for receiving said electrons,means positioned between said beam providing means and said receiving means, and including :an electrode assembly'for periodically deflecting the electron beam, said assembly includinga pair'of conducting platelike members spaced apart to provide a passageway t herebetween, said plate-like members having oppositely disposed'portions removed-to provide open spaces for receiving deflecting electrodes, and deflecting electrodes mounted within said open spaces.

viding means.

ends of said plates removed ;from said beam pro- ,13. An electron discharge devic havin a cathode for supplying a directed beam :of electrons, and another electrode for receiving said electrons, and :means positioned between said cathode and saidreceiving electrode and includof said plates for maintaining ;said,:p1ates ;in

spaced relationship, and oppositely disposednde- .flecting electrodes registering with said open spaces in said plates.

14. An electron discharge device having a cathode for supplying a directed beam of electrons, and another electrode 'for receiving said electrons, and means positioned between said cathode and said receiving electrode and including an electrode assembly for periodically deflecting said electron beam said'assem'bly including a pair of parallel side plates provided with oppositely disposed registering open spaces therein, portions on said plate extending toward each other in registering relationship-for providing a restricted passageway for said beam, separating elements positioned at opposite ,edges of said plates for maintaining said plates in spaced relationship, oppositely disposed deflecting electrodes registering with the open spaces in said plates, and a rod-like element positioned between the planes of said plates adjacent the ,receiving electrode end of said plates.

NORVAL H. GREEN. WILLIAM HOYT -WARREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED ,STATES UPA'IENTIS Number Name Date 1,910,560 Norinder "May23, 1933 2,093,876 Von Ardcnne Sept.i2l, .1937 2,332,622 'Galbick Oct.26, 1943 2,233,795 Pensak Mar. 4, 1941 2268,195 *Winans Dec.30,, 1941 2,294,659 'Herold :Sept. :1, .1942 

